2. Hardware Reference

Chapter 2 describes the hardware components and principal hardware subsystems of the RCM2200. Appendix A, "RabbitCore RCM2200 Specifications," provides complete physical and electrical specifications.

2.1 RCM2200 Digital Inputs and Outputs

Figure 1 shows the subsystems designed into the RCM2200.

Figure 1. Rabbit Subsystems

The RCM2200 has 26 parallel I/O lines grouped in five 8-bit ports available on headers J4 and J5. The 16 bidirectional I/O lines are located on pins PA0-PA7, PD3-PD5, and PE0-PE1, PE4, PE5, and PE7. The pinouts for headers J4 and J5 are shown in Figure 2.

Figure 2. RCM2200 I/O Pinouts

2.1.1 Dedicated Inputs

PB0 is a general CMOS input when the Rabbit 2000 is either not using Serial Port B or is using Serial Port B in an asynchronous mode. Four other general CMOS input-only pins are located on PB2-PB5. These pins can also be used for the slave port. PB2 and PB3 are slave write and slave read strobes, while PB4 and PB5 serve as slave address lines SA0 and SA1, and are used to access the slave registers. PC1 and PC3 are general CMOS inputs only. These pins can instead be selectively enabled to serve as the serial data inputs for Serial Ports D and C.

2.1.2 Dedicated Outputs

One of the general CMOS output-only pins is located on PB7. PB7 can also be used with the slave port as the /SLAVEATTN output. This configuration signifies that the slave is requesting attention from the master. PC0 and PC2 are also output-only pins; PC0 and PC2 can instead serve as the serial data outputs for Serial Ports D and C.

2.1.3 Memory I/O Interface

Four of the Rabbit 2000 address lines (A0-A3) and all the data lines (D0-D7) are available. I/0 write (/IOWR) and I/0 read (/IORD) are also available for interfacing to external devices.

The ports on the Rabbit 2000 microprocessor used in the RCM2200 are configurable, and so the factory defaults can be reconfigured. Table 1 lists the Rabbit 2000 factory defaults and the alternate configurations.

Table 1. RCM2200 Pinout Configurations

Pin		Pin Name	Default Use	Alternate Use	Notes
Header J4	1	GND
	2	VCC
	3	PC0	Output	TXD
	4	PC1	Input	RXD
	5	PC2	Output	TXC
	6	PC3	Input	RXC
	7	TPOUT-			Ethernet transmit port
	8	TPOUT+
	9	LNK			Ethernet link (LNK) LED indicator
	10	PD3	Bitwise or parallel programmable I/O
	11	PD4		ATXB output
	12	PD5		ARXB input
	13	/IORD	Input (I/O read strobe)
	14	/IOWR	Output (I/O write strobe)
	15	PE0	Bitwise or parallel programmable I/O	I0 control or INT0A input
	16	PE1		I1 control or INT1A input
	17	TPIN-			Ethernet receive port
	18	TPIN+
	19	PE4	Bitwise or parallel programmable I/O	I4 control or INT0B input
	20	PE5		I5 control or INT1B input
	21	ACT			Ethernet active (ACT) LED indicator
	22	PE7	Bitwise or parallel programmable I/O	I7 control or slave port chip select /SCS
	23-26	A[3:0]			Rabbit 2000 address bus
Header J5	1-8	PA[0:7]	Bytewide programmable parallel I/O	Slave port data bus SD0-SD7
	9	/RESET	Reset output	Reset input	This weak output can be driven externally
	10	PB0	Input	Serial port clock CLKB input or output
	11	PB2	Input	Slave port write /SWR
	12	PB3	Input	Slave port read /SRD
	13	PB4	Input	SA0	Slave port address lines
	14	PB5	Input	SA1
	15	PB7	Output	Slave port attention line /SLAVEATTN
	16-23	D[7:0]	Input/Output		Rabbit 2000 data bus
	24	VBAT	3 V battery input
	25	VCC
	26	GND

2.1.4 Other Inputs and Outputs

As shown in Table 1, pins PA0-PA7 can be used to allow the Rabbit 2000 to be a slave to another processor. The slave port also uses PB2-PB5, PB7, and PE7.

PE0, PE1, PE4, and PE5 can be used for up to two external interrupts. PB0 can be used to access the clock on Serial Port B of the Rabbit microprocessor. PD4 can be programmed to be a serial output for Serial Port B. PD5 can be used as a serial input by Serial Port B.

PC4, PC5, PD0, PD1, PE2, PE3, and PE6 are used for internal communication with the RealTek Ethernet interface chip.

2.2 Serial Communication

The RCM2200 board does not have an RS-232 or an RS-485 transceiver directly on the board. However, an RS-232 or RS-485 interface may be incorporated on the board the RCM2200 is mounted on. For example, the Prototyping Board supports a standard RS-232 transceiver chip.

2.2.1 Serial Ports

There are four serial ports designated as Serial Ports A, B, C, and D. All four serial ports can operate in an asynchronous mode up to the baud rate of the system clock divided by 64. An asynchronous port can handle 7 or 8 data bits. A 9th bit address scheme, where an additional bit is sent to mark the first byte of a message, is also supported. Serial Ports A and B can also be operated in the clocked serial mode. In this mode, a clock line synchronously clocks the data in or out. Either of the two communicating devices can supply the clock. When the Rabbit 2000 provides the clock, the baud rate can be up to 80% of the system clock frequency divided by 128, or 138,240 bps for a 22.1 MHz clock speed.

Serial Port A is available only on the programming port, and so is likely to be inconvenient to interface with.

2.2.2 Ethernet Port

Figure 3 shows the pinout for the RJ-45 Ethernet port (J2). Note that some Ethernet connectors are numbered in reverse to the order used here.

Figure 3. RJ-45 Ethernet Port Pinout

Two LEDs are placed next to the RJ-45 Ethernet jack, one to indicate an Ethernet link (LNK) and one to indicate Ethernet activity (ACT).

The Ethernet signals are also available on header J4. The ACK and LNK signals can be used to drive LEDs on the user board the RCM2200 is connected to.

The transformer/connector assembly ground is connected to the RCM2200 printed circuit board digital ground via a 0 W resistor, R29, as shown in Figure 4.

Figure 4. Isolation Resistor R29

The RJ-45 connector is shielded to minimize EMI effects to/from the Ethernet signals. Z-World recommends that an equivalent RJ-45 connector be used on the user board if the customer wishes to have an RJ-45 connector on the user board.

NOTE	The RCM2210 is available without the LEDs and the RJ-45 con--nector if you plan to use your own RJ-45 connector on your user board.

2.2.3 Programming Port

Serial Port A has special features that allow it to cold-boot the system after reset. Serial Port A is also the port that is used for software development under Dynamic C.

The RabbitCore RCM2200 has a 10-pin program header labeled J1. The Rabbit 2000 startup-mode pins (SMODE0, SMODE1) are presented to the programming port so that an externally connected device can force the RCM2200 to start up in an external bootstrap mode. The Rabbit 2000 Microprocessor User's Manual provides more information related to the bootstrap mode.

The programming port is used to start the RabbitCore RCM2200 in a mode where it will download a program from the port and then execute the program. The programming port transmits information to and from a PC while a program is being debugged in-circuit.

The RabbitCore RCM2200 can be reset from the programming port via the /RESET_IN line.

The Rabbit 2000 status pin is also presented to the programming port. The status pin is an output that can be used to send a general digital signal.

The clock line for Serial Port A is presented to the programming port, which makes synchronous serial communication possible.

2.2.3.1 Alternate Uses of the Programming Port

The programming port may also be used as an application port with the DIAG connector on the programming cable.

All three clocked Serial Port A signals are available as

• a synchronous serial port

• an asynchronous serial port, with the clock line usable as a general CMOS input

• two general CMOS inputs and one general CMOS output.

Two startup mode pins, SMODE0 and SMODE1, are available as general CMOS inputs after they are read during the initial boot-up. The logic state of these two pins is very important in determining the startup procedure after a reset.

/RES_IN is an external input used to reset the Rabbit 2000 microprocessor.

The status pin may also be used as a general CMOS output.

See Appendix E, "Programming Cable," for more information.

2.3 Other Hardware

2.3.1 Clock Doubler

The RCM2200 takes advantage of the Rabbit 2000 microprocessor's internal clock doubler. A built-in clock doubler allows half-frequency crystals to be used to reduce radiated emissions. The 22.1 MHz frequency is generated using an 11.0592 MHz crystal. The clock doubler is disabled automatically in the BIOS for crystals with a frequency above 12.9 MHz.

The clock doubler may be disabled if 22.1 MHz clock speeds are not required. Disabling the Rabbit 2000 microprocessor's internal clock doubler will reduce power consumption and further reduce radiated emissions. The clock doubler is disabled with a simple change to the BIOS as described below.

1. Open the BIOS source code file, RABBITBIOS.C in the BIOS directory. 2. Change the line #define CLOCK_DOUBLED 1 // set to 1 to double the clock if XTAL<=12.9MHz, to read as follows. #define CLOCK_DOUBLED 0 // set to 1 to double the clock if XTAL<=12.9MHz, 3. Change the serial baud rate to 57,600 bps when the RabbitCore RCM2200 is operated at 11.05 MHz. 4. Save the change using File > Save.

2.4 Memory

2.4.1 SRAM

The RCM2200 is designed to accept 32K to 512K of SRAM packaged in an SOIC case.

The existing standard models of the RCM2200 come with 128K or 512K of SRAM. Figure 5 shows the locations and the jumper settings for the jumpers at JP7 used to set the SRAM size. The "jumpers" are 0 W surface-mounted resistors.

Figure 5. RCM2200 Jumper Settings
for SRAM and Flash EPROM Size

2.4.2 Flash EPROM

The RCM2200 is also designed to accept 128K to 512K of flash EPROM packaged in a TSOP case.

The existing standard models of the RCM2200 come with one or two 256K flash EPROM. There is room at U7 for a third flash EPROM, but this configuration is not presently available as a standard RCM2200 version. Figure 5 shows the locations and the jumper settings for the jumpers at JP1, JP4, and JP6 used to set the flash EPROM size. The "jumpers" are 0 W surface-mounted resistors.

NOTE	Z-World recommends that any customer applications should not be constrained by the sector size of the flash EPROM since it may be necessary to change the sector size in the future.

A Flash Memory Bank Select jumper configuration option based on 0 W surface-mounted resistors exists at JP2, JP3, and JP5 (corresponding to the flash memory chips at U8 [second flash on RCM2250], U3 [RCM2200], and U7 [no flash installed on existing RCM2200 versions]). This option, used in conjunction with some configuration macros, allows Dynamic C to compile two different co-resident programs for the upper and lower halves of the 256K flash in such a way that both programs start at logical address 0000. This is useful for applications that require a resident download manager and a separate downloaded program. See Application Note 218, Implementing a Serial Download Manager for a 256K Flash, for details.

2.4.3 Dynamic C BIOS Source Files

The Dynamic C BIOS source files handle different standard RAM and flash EPROM sizes automatically.